Many organic polymers, more particularly halogen containing organic polymers are conveniently and economically processed into useful articles of commerce by methods employing heat to melt or soften the polymer. The use of such heat can be and often is detrimental to the polymer, especially where the polymer is exposed to high (e.g. 350.degree. to 400.degree. F.) processing temperatures for any extended period of time (e.g. several minutes up to about 30 minutes). It is well known that many organic polymers, including halogen containing organic polymers, will undergo color changes and various other physical changes upon exposure to high temperatures over a period of time unless properly protected. The color change is gradual but visually perceptable during short (e.g. 1 to 8 minutes) term exposure to high processing temperatures. However, with extended (e.g. 10 to 30 minutes) exposure to high processing temperatures the change in color accelerates and becomes greater in intensity. Color changes occuring during the first several minutes (e.g. 1 to 5 minutes) of exposure to high processing temperatures are commonly referred to as early color or early discoloration. Avoidance of such early color or early discoloration is notably important in a number of applications (e.g. plastic pipe) and is particularly important where white or light colored products are to be produced. It is of course also important to prevent or reduce discoloration and deterioration of the organic polymer during extended exposure to high processing temperatures as may be encountered in some processes or fabricating methods.
To prevent or reduce the discoloration and deterioration of organic polymers, more particularly thermoplastic organic polymers, during processing at elevated temperatures and during exposure of the fabricated product to elevated temperatures under use conditions the art has added various materials to the polymers. Among these materials added to the polymer are substances referred to as stabilizers. Included among these stabilizers used by the art are organic antimony compounds [e.g. antimony tris (alkyl mercaptide)]. Although various organic antimony compounds have been taught in the art for heat stabilizing organic polymers, more particularly halogen containing polymers and still more particularly vinyl halide polymers (e.g. PVC), the organic antimony compounds as heat stabilizers have been found to be less effective than many other stabilizers (e.g. organotin stabilizers). This lower effectiveness in heat stabilizing organic polymers, particularly vinyl halide polymers, has made the organic antimony compounds of the art unattractive for commercial application, even though in many instances organic antimony compounds have a cost advantage over other stabilizers. Thus, there continues to exist a need and advantage for improving the stabilizing effectiveness of organic antimony stabilizers.
A number of the well-known organic antimony stabilizers are unstable to moisture and light (e.g. ultraviolet light). This instability toward moisture and light is particularly noted with organic antimony stabilizers having an antimony to sulfur to carbon (i.e. Sb-S-C) bond [e.g. antimony tris (isooctylthioglycolate)]. On exposure of the organic antimony stabilizer to water (e.g. moisture) there are often formed insoluble or incompatible products thereby producing a heterogeneous organic antimony stabilizer composition and reducing the effectiveness of the organic antimony stabilizer in heat stabilizing an organic polymer, particularly a vinyl halide polymer. This heterogeneity and reduced effectiveness in heat stabilizing organic polymers contributes to making such stabilizers less useful and commercially unattractive. Organic antimony stabilizers can upon exposure to ultraviolet (U.V.) light discolor and/or form a precipitate thereby indicating deterioration of the organic antimony stabilizer. In some cases the discoloration and/or precipitation, upon exposure to UV light, occurs within from one to a few hours. This discoloration and/or precipitation seriously impairs the usefulness and acceptability of such organic antimony stabilizers. It is therefore desirable to overcome these disadvantages and provide highly stable and highly effective organic antimony stabilizers. Desirably, it would be highly advantageous to both overcome the stability disadvantages and the lower stabilizing activity of the art organic antimony stabilizers.